A PCIe bus is a high-performance system bus applied in computers and communication platforms. In the existing technology, communication status of two communication parties that interact on a PCIe bus is defined. Because two parties communicating with each other, having interface modules acting as a transmitting end and a receiving end respectively, are connected through an electrical cable, a differential-mode voltage of the transmitting end is basically the same as a differential-mode voltage of the receiving end. If the differential-mode voltage of the receiving end is below 65 mV (millivolt), the receiving end determines that the transmitting end is in an electrical idle state. If the differential-mode voltage of the receiving end ranges between 65 mV and 175 mV, the receiving end determines that a noise signal is transmitted by the transmitting end. If the differential-mode voltage of the receiving end is above 175 mV, the receiving end determines that a normal signal is received and it decodes this signal.
In order to improve transmission rate and quality between the two communication parties, in the existing technology, an optical fiber may be adopted to connect the transmitting end with the receiving end. Because the signal output by the transmitting end is an electrical signal, optical modules (implemented by hardware circuits) need to be installed at the transmitting end and the receiving end respectively. The optical module at the transmitting end converts the electrical signal into an optical signal, and after the optical signal is transmitted to the receiving end, the optical module at the receiving end converts the optical signal back into an electrical signal.
However, when the two communication parties communicate through an optical fiber, even if the differential-mode voltage of the transmitting end is below 65 mV, due to light emission characteristics of the optical modules, the differential-mode voltage received at the receiving end may still be above 175 mV. This leads the receiving end to regard the noise output from the transmitting end as a normal signal. Therefore an abnormality in optical fiber communication may occur when the transmitting end is in an electrical idle state or outputs noises.